The subject application is directed generally to black replacement in connection with primary color schemes. The application is particularly suited to provide users with prompt feedback relative to black replacement under various black-width replacement strategies.
Color images are generated by selectively combining primary colors from a selected color space. There are two basic types of primary colors, additive and subtractive. Additive colors are typically used in active light generation devices, such as projectors or displays. A common additive color space for such devices is comprised of red, green, and blue (RGB), which can be selectively combined to generate most colors recognized by the human eye. A positive combination of all colors generates light that is perceived as white.
A subtractive color space is used to selectively remove colors from a composite light source, such as white light. Subtractive primaries are typically used to generate color images on passive material, such as paper. Inks or dyes from a subtractive color space, such as cyan, magenta, and yellow, may be selectively applied to a medium, such as paper, to generate color images. Current devices, such as workstations, typically include both active devices, such as a display, and passive devices, such as a printer. An electronic image is suitably viewed or manipulated on a display, and a printout is made on a color printer. It will be appreciated that to do such, an image must be represented in both active and passive color spaces.
The total amount of colors that can be realized by various primary colors is referred to as a gamut. A gamut of a CMY color space can be extended by the addition of a black colorant. Addition of black (K) results in a color space referred to as CMYK. Certain colors in CMYK color space can be realized with the CMY components, or alternatively realized by a substitution of black.
In color profiles, such as profiles formatted in connection with the International Color Consortium (ICC), a black generation method may be chosen at a time when a profile is created. It is often desirable to determine a black replacement strategy which is optimal for a particular image or a particular physical rendering device. A user suitably specifies a range for black replacement. This is suitably specified by specifying a start value, a maximum value, or a width for black replacement. A black start value is suitably thought of as an amount of black ink where black starts replacing other inks. A maximum value is suitably defined as to how high the black level is permitted to be for a resulting color. A black width is suitably defined as to how far into saturated colors black replacement is permitted. A low black width will, for example, limit black substitution to near-neutral colors, while a high black width will allow substitutions further into saturated colors.
An optimal black width setting needs to be determined for particular cases. If saturated colors appear to be muddy, this may be an indication that black width should be lowered. Given the complexity of generating visual feedback relative to various black width options, it is generally not practicable to give rapid feedback once adjustments are made.